The 2C9.G3 (HMb3-1) monoclonal antibody reacts with mouse and rat CD61, also known as the integrin β3. CD61 is expressed by activated T cells, granulocytes, and platelet. CD61 associates non-covalently with two integrin α subunits; αV (CD51) to form Vitronectin Receptor and αIib (CD41) to form gpIIb/IIIa. These heterodimeric complexes are responsible for adhesion to extracellular matrix components including fibrinogen, fibronectin, fibronectin, vitronectin, thrombospondin and von Willebrand factor.